Relay stations (RS) or relay nodes (RN) have been proposed as coverage extensions in cellular systems since several years ago.
Apart from this main goal of coverage extension, the introduction of relay concepts is also considered to be beneficial in the provision of high-bit-rate coverage in high shadowing environment, in the reduction of the average radio-transmission power at a user equipment (UE), thereby leading to long battery life, in the enhancement of cell capacity and effective throughput such as increasing cell-edge capacity and balancing cell load, and in the enhancement of the overall performance and cost-effectiveness of radio access networks (RAN).
After a careful consideration in pre-standardization activities like the wireless world initiative (WWI) and the wireless world initiative new radio (WINNER), relay systems are today approaching the level of maturity that is needed in ongoing standardization activities. The best evidence of this maturity is the 802.16j standardization of the institute of electrical and electronics engineers (IEEE) where relays are added on top of the IEEE 802.16e standard.
This recent development has increased the pressure to consider relays also in the standardization of long term evolution (LTE) networks which is even stronger due to the expectation of some operators that relay systems will be economically viable due to reduced backhaul and site acquisition costs.
In order to keep LTE competitive it is more than probable that relay extensions to LTE are to be studied within the 3rd generation partnership project (3GPP) in release 9. That is, it is expected that relaying plays an important role. It is considered that the goal is to have relays included in the release 9 agenda.
FIG. 1 illustrates a typical deployment scenario of a LTE radio access network (RAN) with possible radio relayed extensions as described above.